Final model and regression results for factors contributing to the presence and absence of decay in live (Q. virginiand) and laurel (Q. laurifolia) oak street trees in Tampa, Florida, U.S.
| Variable | Coefficient | Standard error | P-value | Odds ratio | 95% CI lower | 95% CI upper |
|---|---|---|---|---|---|---|
| Intercept | −9.4998 | 2.4854 | 0.0001 | -- | −14.8845 | −4.8744 |
| Visual decay | 0.8511 | 0.3944 | 0.0309 | 2.3422 (D)z | 0.0835 | 1.6374 |
| Species–live oak | −1.8477 | 0.3672 | 0.0012 | 6.3452 (S) | −1.9162 | −0.4707 |
| Tree diameter | 0.3394 | 0.0977 | 0.0005 | 1.4041 (D) | 0.1592 | 0.5581 |
| Tree diameter2 | −0.0034 | 0.0012 | 0.0036 | 1.0034 (S) | −0.0062 | −0.0013 |
| Tree diameter3 | 1.1060 × 10−5 | 4.3750 × 10−6 | 0.0114 | <1.0001 (D) | 3.3932 × 10−6 | 2.1927 × 10−5 |
↵z Positive coefficients indicate an increased likelihood of decay (D). Negative coefficients indicate an increased likelihood of sound wood (S). Odds ratios have been added for ease in interpretation. For example, a live oak tree is more than six times more likely to be completely sound than a laurel oak. For the three tree diameter predictor variables, likelihood of decay increases/decreases with each centimeter diameter is increased.